This invention is based on my disclosure document No. 075,160 filed Oct. 20, 1978.
Today upward of 10.sup.4 transistors can be put on a chip of silicon 1/10 inch square. Fairly straightforward extensions of present technology should make it possible to put 10.sup.5 transistors and similar devices on a chip within the next few years. The reduction in circuit size already achieved has had two major benefits: a sharp decrease in the cost of logic chips and a sharp increase in the speed with which logic operations can be performed. The present state of the art of monolithic logic chips can be seen in the collection of articles appearing in the Special Issue on Microelectronics of the September 1977 issue of Scientific American. Logic chips are also called integrated circuit IC chips.
Although the present trends to build more complex computers, minicomputers and microcomputers lie in the fabrication process of logic chips, the task of interconnecting or interfacing chips has not kept pace with the circuit density of chips. For example, the design of a computer begins with the determination of the overall organization of the computer, i.e., the interconnection and interfacing of logic chips. The "width" of the machine, or in other words the number of bits in a standard word, is a fundamental consideration; so is the amount of memory to be addressed, which dictates the number of address bits that must be provided. Among the multitude of other considerations, attention must be given to the total number of connections to be made to each chip; each connection requires a metallic pad at the edge of the chip, and there is limited room for these pads (peripheral terminals).
Consider a single logic chip, for example the one shown on the cover of the foregoing Special issue of Scientific American. Arrayed around the chip are 40 leads that connect it with other similar chips in a more elaborate architecture of a modern computer. Typically, the logic chip might represent a read only memory (ROM), random access memory (RAM), a multiplier, adder, subtractor, or even a combination of same, for example as in a monolithic (single chip) microprocessor. Clearly, as shown in the cover picture, the 40 metallic pads at the edge of the chip (plus their associated on-chip buffers, etc.) might account for as much as thirty percent (30%) of the total chip area. Thus, if a chip of silicon is 1/10 inch square then 30% of the area of the chip is devoted to interconnecting and interfacing the chip with its external environment, i.e., with other chips in the computer. Significantly, while the chip area devoted to logic circuits is being drastically reduced by the dramatic increase of circuit density, the remaining area of the chip devoted to interconnecting and interfacing the chip has remained relatively constant. It is the purpose and object of this invention to provide apparatus and method which reduces the areas of logic chips devoted to interfacing chips and which materially reduces the number of wire interconnects between chips in a computer.